The following background information may present examples of specific aspects of the prior art (e.g., without limitation, approaches, facts, or common wisdom) that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon.
Metal detectors are used for many applications including detecting land mines, geophysical prospecting, treasure hunting and construction.
Some conventional wire detectors are used for detecting the presence and location of a conductor which extends on opposite sides of a water/air boundary. For example, in the case of a command control wire leading from a location on a bank of a body of water, to a mine situated in the water. These detection systems rely on the coupling between a radio frequency transmitter, which may be located some distance away or carried as a mobile unit aboard a suitable land, water or air vehicle, to couple a signal into the portion of the wire above the water. The above water portion serves as a receiving antenna, which results in the underwater portion acting as a transmitter, where the received signal is retransmitted into the surrounding water medium.
Other conventional cable and pipe locators use up to three different methods to apply a signal to the object. The conductive method applies the signal directly to one end of the cable or wire, while the other end is grounded. The inductive clamp method uses a clamp with jaws which close around the conductor to inductively couple the transmit signal into the object, while the other end is grounded. The inductive method uses a separate transmitter placed directly over the buried cable to induce a signal into any nearby conductors, and is located 13 to 15 meters away from the receiver to reduce false signals coupled through the air. These methods typically rely on the operator having direct contact with the conductor to connect a signal or clamp, or having some idea of where the conductor is buried to position the transmitter.
Some conventional orthogonal coil configurations are composed of turns of wire forming the inductor coils wrapped around a mass of material and bonded to the mass such that the coils becomes deformed responsive to the deformation of the mass. The axial height of one coil approximately equals the width of the other coil on the sides where the coils cross. A third auxiliary coil with some form of external adjustment is used to reduce the coupling between the transmit coil and receive coil to achieve a balanced condition. The three coils are typically of the same size and shape. The wide cross sectional area of the transmit coil produces a weak magnetic field across a wide area.
Elongated objects which have a small cross sectional areas and minimal metallic content, in particular landmine tripwires, are often difficult to detect and to determine the location of De-mining teams face considerable danger when trying to locate tripwire activated landmine wires, as the tripwires are typically located above the ground and may be obscured from vision by foliage. Conventional methods used to indicate the presence of tripwires concealed by foliage include the use of a feeler stick used to prod into the foliage and slowly raised to feel for the presence of a tripwire.
In view of the foregoing, it is clear that these traditional techniques are not perfect and leave room for more optimal approaches.
Unless otherwise indicated illustrations in the figures are not necessarily drawn to scale.